This invention relates to passivating devised particularly though not solely for use in passivating devices used in measuring; or controlling temperature e.g. in the flow of gases from a humidifer to a hospitalised patient using such a humidifer and for similar purposes.
Depending on the environment it may be necessary to shield or passivate a device e.g. a pace maker implanted in a human being to control his heart function or to passivate a thermometer used to monitor temperatures of a gas in the presence of molecular water vapour, e.g. used in the connecting tube between the patient and a humidifier where the water vapour is 100% RH air at 37.degree. C. Various procedures for passivation have been proposed but none have been found to be really satisfactory. The normal process for passivation of a thermistor is by coating it with glass, but this is not satisfactory, since it is a high temperature process and the pre-selected characteristics of interchangeable thermistors may be altered by the process. An alternative coating often used is a thin epoxy layer which may not provide adequate protection to the device and for example epoxy is liable to degradation by body fluids when used for the passivation of a pacemaking device for heart control when embedded in a human being. Furthermore in some types of devices e.g. thermal sensing devices, including those which sense the temperature in the connecting tube above referred to, it is desirable to have a fast response requiring a small thermal mass of the sensor and low thermal resistance between the sensor and the environment. Any additional passivation according to present methods usually result in an increased time constant because of increase in thermal mass and a higher thermal resistance.
It is an object of the invention in one aspect to provide a simple low cost and effective device which will obviate or minimise the foregoing disadvantages in a simple yet effective manner or which will at least provide the public with a useful choice.